The monster are coming and they would want to eat all the people in the kingdom. Fortunately, the castle has lots of protectors to whom the country defends upon. They won't anything to happen to the people of the nation. The idea here is to properly place the protectors to where they could get the most monster. Each kill would earn you money and you can use it to upgrade your protectors. Your protectors accumulate experience by fighting monster and as they reach a certain level, they begin to glow, which mean that they are ready to be upgraded.